The rarest MOT failures in the UK
There are 729 different reasons a vehicle can fail its MOT. Most of them (worn suspension bushes, bald tyres, blown bulbs) happen millions of times a year. But at the other end of the scale, seven defects were recorded exactly once across all 58 million tests in 2024. Here's what they are.
The seven: defects that happened exactly once
“Handlebar grips missing”
Recorded on: Toyota Yaris
The Yaris is a supermini. It does not have handlebars. This is a motorcycle-specific failure code applied to a car, almost certainly a data entry error, where the tester selected the wrong item from the defect list. The actual issue was presumably something wrong with the steering wheel or its covering.
This is the spiritual successor to last year's standout: a Toyota MR2 failed for “handlebars excessively deformed or corroded.” Toyota hatchbacks and motorcycle failure codes are apparently a recurring theme. It shows the limits of any dataset built from human data entry across thousands of testing stations.
“Toe-out of the sidecar wheel relative to the motorcycle”
Recorded on: Yamaha XTZ660
A sidecar wheel should be toed in slightly (1–3 degrees toward the bike) to counteract the natural drag of the sidecar. If it's toed out, pointing away from the bike, the outfit pulls hard to the sidecar side and becomes difficult to steer, especially at speed. The XTZ660 Tenere is an adventure bike, an unusual choice for a sidecar, but not unheard of in the touring community.
This was also a one-time failure in 2023 (on a Triumph America). Sidecar geometry is a whole section of the MOT manual that most testers will never need to open. That it appears at all is a testament to the few remaining sidecar enthusiasts on UK roads.
“Forks or fork yoke deformed, fractured or insecure”
Recorded on: VW Trike
The fork yoke (triple clamp) holds the front fork tubes and connects them to the steering head. If it's cracked, bent, or loose, the front end is structurally compromised. VW Trikes are custom-built three-wheelers using air-cooled VW Beetle engines. They're hand-fabricated, often by small workshops, and the front end is typically motorcycle-derived. A fractured fork yoke on a one-off build is more about fabrication quality than factory engineering.
“Speed limiter tamperproof device missing or defective”
Recorded on: Mazda MX-5
Speed limiters are required on certain commercial vehicles and buses, not sports cars. The MX-5 doesn't have a speed limiter that needs a tamperproof device. This is another data entry anomaly: a commercial vehicle failure code applied to a two-seat roadster. The actual issue was presumably something else entirely. But it made the database, and so it makes this list.
“Speed limiter not fitted in accordance with the requirements”
Recorded on: Citroen Relay
Unlike the MX-5 above, this one makes sense. The Citroen Relay is a large panel van that, depending on its weight class, may legally require a speed limiter. EU regulations require speed limiters on vehicles over 3.5 tonnes manufactured after 2005. If the limiter has been removed, bypassed, or was never fitted on a qualifying vehicle, it's a legitimate MOT failure. That only one was caught in 58 million tests suggests this is either very rare or very hard to detect at a standard MOT station.
“A retro-fitted three point belt fitted to a seat on which the leg and frame has not been suitably modified”
Recorded on: Mitsubishi L200
This is about aftermarket seatbelt installations. When a three-point belt is retrofitted to a seat that originally had a lap belt, the seat frame needs reinforcing to handle the different load path. A three-point belt puts upward force on the upper anchor during a crash, and the original seat structure may not be designed for that. The L200 is a pickup truck where rear seats sometimes get modified for commercial use, and someone apparently fitted a three-point belt without reinforcing the seat mounting.
“Control for electronic retarder does not allow gradual variation in effort”
Recorded on: Volkswagen Polo
An electronic retarder is an auxiliary braking system used on heavy commercial vehicles. It slows the vehicle using electromagnetic resistance without touching the service brakes. The Volkswagen Polo does not have an electronic retarder. This is another commercial vehicle code applied to a supermini, and it's genuinely baffling. Whatever was actually wrong with this Polo, it wasn't an electromagnetic braking system that doesn't exist.
What this tells us
The MOT test manual contains hundreds of specific failure codes, many of them designed for vehicle types that are rare on UK roads: sidecars, vehicles with twin wheels, commercial vehicles with speed limiters. When you test 58 million vehicles, you expect most of these codes to be used at least occasionally. But seven of them were used exactly once.
A pattern emerges: at least three of the seven (handlebar grips on a Yaris, speed limiter tamperproof device on an MX-5, electronic retarder on a Polo) are data entry errors, commercial or motorcycle codes applied to cars that don't have the relevant components. The rest are genuinely rare situations: a sidecar with wrong toe angle, a hand-built trike with fractured forks, a van without its required speed limiter, and a pickup with a badly fitted seatbelt.
At the other extreme, over 2 million vehicles failed for worn suspension bushes alone. The mundane stuff (suspension, bulbs, tyres) accounts for the vast majority of all failures. If you want to pass your MOT, look at the common failures, not these outliers.
Almost as rare: failures that happened 2–5 times
17 failure reasons at this level.
Show all
The full scale
729 total unique failure reasons in the MOT testing system. 152 of them (21%) were used fewer than 100 times across all 58 million tests. The MOT system is designed to cover every possible defect on every possible vehicle, including ones that barely exist any more.
MOT data from DVSA anonymised test results, 2024 test year. 58 million tests, 729 unique failure reasons. Crown copyright, OGL v3.0. Pass rates are statistical summaries, not assessments of individual vehicle safety.